What is a weed?

Faced with the old problem today, of "what is a weed?"

Eucalyptus robusta, or swamp mahogany. It's a magnificent looking tree, I've seen one growing down the road from here and they can really look spectacular. However, they are not indigenous to this area. That isn’t too much of an issue in itself, but they have a tendency to through their seeds, and send up little babies everywhere. Again, not too much of an issue, but the real issue is that they have the ability to hybridize with Eucalyptus camaldulensis, which is the quite abundant along the river here.

There is very large swamp mahogany growing right on the waters edge, and the decision was made to leave that one, but the couple that are growing in amongst the river reds have gotta go! 

This one stays.

This one's not so lucky...